A Simple MCP Weather Server written in TypeScript

A minimal MCP server that exposes US weather data from the National Weather Service API as two tools:

• get-forecast – get the forecast for a location (takes latitude and longitude)
• get-alerts – get active weather alerts for a US state (takes a two-letter state code)

This example accompanies the Build an MCP server tutorial.

Prerequisites

• Node.js 24+
• npm

Build and run

npm install
npm run build
node build/index.js

The server communicates over stdio, so running it directly just waits for a client on stdin. To see it in action, launch it from one of the client examples in this repository, for example:

cd ../mcp-client-typescript
npm install && npm run build
node build/index.js ../weather-server-typescript/build/index.js

Structured content

Both tools declare an outputSchema and return structuredContent. get-forecast returns an object; get-alerts returns a top-level JSON array, which protocol revision 2026-07-28 is the first to allow — see Structured Content in the spec.

serveStdio serves both protocol eras from one factory, and the SDK projects the array-rooted schema down to the {"result": [...]} form for a 2025-11-25 client, so adopting it costs older clients nothing. See the SDK documentation.